The present invention relates to the field of tube cutting and more particularly to a tube cutter having an automatic feed as the cutter is rotated for the purpose of cutting through the tube.
A large number of devices exist for rotating a cutter around a tube to cut the tube at the desired position. The present invention relates to a tube cutter wherein the cutter wheel is a wheel biased against the outer surface of the tube to automatically advance or feed the cutter into the tube as the cutter is rotated. A common arrangement for accomplishing this objective is shown in Condon U.S. Pat. No. 2,448,578 and Collier U.S. Pat. No. 5,903,980. A cutter or cutters are carried on a clam shell type frame by a spring element so the clam shell can be assembled over a tube with the cutter biased against the outside surface of the tube. By rotating the frame, the cutter or cutters automatically advances into the tube until the tube is severed. Such devices do not specifically relate to the present invention, but are incorporated by reference herein as background information. Another mechanism for tube cutters having an automatically advanced cutter is illustrated in McDaniel U.S. Pat. No. 5,206,996. A cutter wheel is mounted on a spring biased lever system or is spring biased from one side of a fixed C-shaped frame. This patent is incorporated by reference herein as further background information, even though it does not even disclose the general feeding arrangement used in the present invention.
The invention involves a tube cutter wherein a housing, frame, or jaw supports and forms a cradle for the tube to be cut. An opposite frame, jaw, or arm carries the rotary cutter wheel and slides toward the tube being cut during the cutting operation. The sliding jaw concept for tube cutters is illustrated in Myers U.S. Pat. No. 1,945,949 and Kritchever U.S. Pat. No. 5,495,672 both of which are incorporated by reference herein as teaching the general concept to which the present invention is directed. This general concept is an automatic tube cutter wherein the cutter includes two linearly slidable frames movable together to define the cutting action. The rotary cutting wheel is biased against the tube so that it is automatically advanced as the cutting depth increases during the rotary cutting action.
Tube cutters are well known in the field and are generally constructed to allow movement of the cutting wheel into the tube by manually advancing the cutting wheel inwardly during the cutting operation. Such devices are awkward to use and require constant operator attention, as well as skill. Consequently, it has become somewhat common to provide a tube cutter in which the rotating cutting wheel is automatically fed into the tube as it is being cut. This provides a tube cutter that is easily and quickly positioned for use. Such tube cutter only requires turning of the cutter around the tube in order to complete the cutting operation once the cutter has been positioned on the tube. This rotating action can be manual or can be by a power drive as shown in Kritchever U.S. Pat. No. 5,495,672. The difficulty is that the various structures for accomplishing the automatic feeding of cutting wheel into the tube during the rotating cutting action have advantages, but present distinct disadvantages. For instance, when the automatic advancing cutter is in a clam shell frame, as shown in Condon U.S. Pat. No. 2,448,578 or Collier U.S. Pat. No. 5,903,980, the size of the frame is dictated by the size of the tube being cut. Consequently, each tube size requires its own cutter. The amount of spring force exerted during the cutting operation is dictated by the size of the clam shell frame. Minor differences in the diameter of the tube can not be accommodated in such fixed frame rotary tube cutters. These cutters are thus dedicated tools and can not be used universally. Another type of tube cutter that is generally size specific is shown in McDaniel U.S. Pat. No. 5,206,996. The diameter of the tube being cut dictates the size of the U-shaped frame for carrying the support rollers and the spring biased cutter. With this fixed frame tube cutter, there is no easy way to accommodate different tube sizes. As the spring loses its spring force during long-term use or in temperature changes, the cutting action is drastically affected. This is also true of the encircling frame type of tool. Each of these cutters is tube size specific and susceptible to changes in the spring biased cutter to alter the efficiency and effectiveness of the cutting action. McDaniel recognizes the disadvantage of fixed frame tube cutter by suggesting a tube cutter involving a spring biased lever system wherein one blade of the system carries the support rolls and the other blade carries the rotating cutter wheel. This attempt to rectify the problems associated with a fixed frame tube cutter is not successful for many reasons. It includes protruding handles and a pivoting infeed of the rotating cutter wheel that changes the cutting action and spring force according to the diameter of the tube being cut.
The disadvantages of tube cutters that automatically feed the cutter wheel into the tube during cutting, but are size specific, was generally solved in 1934. In Myers U.S. Pat. No. 1,945,949, a first frame carries the two tube support rollers. The other frame rotates the rotating cutter wheel about a fixed axis and is pulled toward the first frame by a threaded shaft. To load the cutter for automatic feeding, the shaft is connected between the two frames through a coil spring. Movement of the second frame stops when the cutter wheel engages the surface of the tube positioned adjacent the support rollers in the first frame. Thereafter, rotation of the threaded shaft compresses the coil spring to bias the second frame toward the first frame. During the cutting action, as the tool is rotated about the tube, the second frame advances toward the first frame as the depth of cut increases. This action creates automatic feeding for the rotating cutter blade. The tool is not size specific. Sliding of one frame with respect to the other frame with the spring loaded threaded shaft has heretofore proved an extreme benefit over the fixed frame tube cutters described above. Another version of the cutter shown in Myers is illustrated in Kritchever U.S. Pat. No. 5,495,672. The movable jaw or frame carrying the rotating wheel is moved toward the tube cradled by the support rollers on the other frame. The rotating threaded shaft moves the one jaw until it engages and clamps the tube in the cutter. Additional rotation of the threaded shaft compresses an encircling spring to determine the amount of force exerted by the cutter wheel against the tube. After the force has been applied one jaw is biased toward the other jaw to load the rotating cutter wheel for automatic feeding as the cut progresses. This type of cutter can be operated manually or by a power rotating device. Even though there is an advantage for the movable frame type pipe cutters they still have certain disadvantages. The cutting action is controlled by a Belleville spring or a coil spring surrounding the shaft used for sliding one jaw toward the other jaw. Such spring indirectly affects the moving action of the cutter wheel. The wheel movement is also affected by sliding of the two frames together. Dirt and environmental contamination can adversely affect the cutting action. Indeed, in some instances, dirt and contamination in the slide mechanism between the two frames renders this type of cutter inoperative. Since the jaw must be moved by an intermediate spring, it is difficult for the threaded shaft to overcome irregularities in the sliding mechanism. The second frame may be movable into the cutting position, but during the cutting action, it can jerk, freeze or otherwise affect the smoothness and repeatability of the tube cutting operation. Friction irregularities causes jerks, which can affect the uniformity of the cut being made on the tube. All of these disadvantages have resulted in certain operators preferring the fixed frame concept shown in Collier U.S. Pat. No. 5,903,980. Consequently, tube cutters with automatic feeding are either size specific or susceptible to less than optimum cutting action, or both.
The present invention relates to a tube cutter of the type which automatically feeds the cutter wheel into the tube as the cutting operation progresses, without the disadvantage of size specific fixed frame tools or tools that have a metal to metal sliding action during the cutting operation. The automatic feed for the rotating tube cutter is smooth, gradual and continuous without the constraints of a fixed frame tool.
In accordance with the present invention, there is provided a tube cutter for cutting a circular tube having a central axis. This cutter includes a housing with first and second parallel rollers defining a cradle for receiving a tube to be cut, with the two axis generally parallel to the axes of the rollers. The housing forms a first frame. The second frame is a cutter head reciprocally mounted on the housing for sliding linearly in a direction toward and away from the rollers. This second frame, or cutter head, includes an upstanding arm supporting a cutter wheel rotatable about an axis generally parallel to the axes of the rollers and facing the tube as it is received in the cradle defined by the rollers. As so far described, the invention is similar to prior adjustable frame tube cutters. One frame slides linearly with respect to the other frame to accommodate different tube sizes. In accordance with the invention, a spring element is used to mount the cutter wheel onto the head or second frame, thus biasing the cutter wheel in the direction of movement of the second frame as it moves toward the support rollers. A threaded shaft between the housing, or first frame, and the cutter head, or second frame, is rotatable to move the cutter head linearly toward and away from the housing. The threaded shaft does not have an intermediate connection by way of an encircling spring, such as a coil spring or Belleville spring. There is positive movement of one frame on the other frame in a linear sliding action. This movement is under the direct control of the thread and is not affected adversely by contamination, dirt or other obstructions which must be overcome by the manual rotation of the threaded shaft. The invention allows the second frame to be moved toward the first frame until the cutter wheel engages the tube. Then, the spring element is deflected to create a cutting force pushing the wheel against the tube for the cutting action. In the preferred embodiment of the invention, the cutter wheel is carried by a shaft that is movably mounted with respect to the second frame, or upstanding arm, so that the spring element can be a spring between the cutter support shaft and the inwardly moving arm or frame. The force biasing the cutter wheel toward the tube is dictated by only the spring constant of the intermediate spring supporting the rotating cutter wheel. There is no sliding action needed to cut the tube. A secondary application of the present invention is the provision of a cutter wheel rotatably mounted on the upstanding arm of the second frame. To accomplish the springing action, the arm has a flexible section between the cutter and the remainder of the second frame. In this alternative embodiment of the invention, the second frame is moved toward the first frame to capture the tube. Rotation of the threaded shaft further deflects the resilient flexible portion of the arm to apply a biasing force or load on the wheel for automatic feeding during the cutting operation. This second embodiment is not the preferred embodiment, but is an alternative tool using the invention.
The primary object of the present invention is the provision of a tube cutter using an automatic feed feature, which cutter is not size specific.
Another object of the present invention is the provision of a tube cutter, as defined above, which tube cutter has a smooth uniform cutting action that is not affected by contamination, dirt and/or obstructions capable of affecting a smooth sliding action between two metal frames.
Yet another object of the present invention is the provision of a tube cutter, as defined above, which tube cutter overcomes the disadvantage of a fixed frame tube cutter and the disadvantages of an adjustable frame tube cutter, while maintaining the capability of automatically feeding the rotating cutter wheel into the tube during the cutting.
Still a further object of the present invention is the provision of a tube cutter, as defined above, which tube cutter utilizes a unique and novel spring for biasing the cutting wheel toward the tube.
Another object of the present invention is the provision of a tube cutter, as defined above, which tube cutter utilizes a movable frame concept where the frames are in a fixed position during the cutting operation.
These and other objects and advantages will become apparent from the following description taken together with the accompanying drawings.